1. Technical Field
The present disclosure relates to a toner for use in electrophotographic or electrostatic recording apparatuses. The present disclosure also relates to a one-component or two-component developer, an image forming apparatus, and a process cartridge each using the above toner.
2. Description of Related Art
A typical electrophotographic method includes an electrostatic latent image forming process in which an electrostatic latent image is formed on a photoreceptor including a photoconductive substance; a developing process in which the electrostatic latent image is developed into a toner image with a toner; a transfer process in which the toner image is transferred onto a transfer material such as paper; a fixing process in which the toner image is fixed on the transfer material by application of heat, pressure, and/or solvent vapor; and a cleaning process in which residual toner particles remaining on the photoreceptor are removed.
Generally, a toner includes a particulate material having an average primary particle diameter of several to several tens nanometer at its surface so as to improve surface properties of the toner. Such a particulate material being present at or covering the surface of a toner may be hereinafter referred to as an “external additive”. As an example of the external additive, particulate hydrophobized silicas have been proposed that give chargeability, fluidity, and hydrophobicity to toner. As another example of the external additive, particulate hydrophobized titanium oxides have been proposed that keep chargeability of toner and prevent fluctuation of retaining charge quantity of toner regardless of environmental temperature and humidity conditions.
JP-2007-248911-A describes a toner including a colored particle, an external additive, and an organic particle having a weight average particle diameter of 2 to 15 μm and pores on its surface.
JP-2007-156099-A describes a toner including a particulate hydrophobized material as an external additive to have a certain specific surface area.
JP-2008-116568-A describes a toner including a specific amount of a structure comprised of a crystalline polyester resin and a release agent.
JP-2007-279702-A describes a toner including a non-spherical irregular-shaped silica (having a long diameter of 40 to 120 nm) as an external additive.
JP-2000-19753-A describes a toner including a first inorganic particulate material having a particle diameter of 0.1 μm or less and a second inorganic particulate material having a particle diameter of 0.12 to 3.0 μm.
As described above, various types of external additives have been proposed for the purpose of reliably improving performance of electrophotographic processes. At the same time, toner particles themselves have been developed for the purpose of improving performance, printing speed, and lifespan of electrophotographic processes. For example, one proposal for improving fixability of toner involves making wax particles present at the surface of the toner and another proposal involves including a crystalline material in the toner that requires less melting energy.
However, these proposals may cause another problem such that the wax or crystalline material films a photoreceptor with its thin layer (“filming problem”) to degrade image quality.